The present nonprovisional application claims priority under 35 USC 119 to Japanese Patent Application No. 2001-362891 filed on Nov. 28, 2001 and Japanese Patent Application No. 2002-281994 filed on Sep. 26, 2002 the entire contents thereof are hereby incorporated by reference.
1. Field of the Invention
The invention relates to a fuel injection apparatus for an engine, and more specifically, to a structure of pressure regulating means for regulating the fuel pressure constant and a pressure regulating valve constructing the same.
2. Description of Background Art
FIG. 6 shows an example of a pressure regulating circuit in a fuel injection apparatus in the related art, in which a reflux passage 3 is connected to an end of a fuel injection passage 2 to which a plurality of injectors 1 are connected. A pressure regulating means 4 is provided in this reflux passage 3 which opens the pressure regulating valve that constitutes the pressure regulating means 4 to return fuel from an exit 5 into a fuel tank 6 and controls the fuel pressure in the fuel injection passage 2 to a predetermined pressure when the fuel pressure in the fuel pressure injection passage 26 reaches or exceeds a predetermined value.
Fuel in this case is pumped from the fuel tank 6 to the other end of the fuel injection passage 2 by a fuel pump 7. The pressure regulating valve constituting the pressure regulating means 4 forms a closed space by putting a cap 9 on the housing 8 which is integral with the reflux passage 3. Thus, the interior of this closed space and the reflux passage 3 are in communication with each other through an entrance 8a provided on the housing 8. A valve body 10 is provided in the interior of the closed space for opening and closing a seat 11 which corresponds to an entrance of the pressure regulating valve, and is supported by a diaphragm 12 clamped between the housing 8 and the cap 9 around its outer periphery, so that the valve body 10 is pressed against the seat 11 by a spring 13 at a predetermined load.
The cap 9 is provided with a negative pressure pipe 14 for connecting an air chamber 15 on the cap 9 side defined by the diaphragm 12 and the intake passage of an engine, which is not shown in FIG. 6, so that the valve body 10 is opened by the depression at engine manifold by decreasing the pressure in the air chamber 15 to a negative pressure by a control means when the fuel pressure in the fuel injection passage 2 is increased to the pressure over a predetermined value. The internal space in the housing 8 defines a liquid chamber 16 blocked out from the air chamber 15 by a diaphragm 12, which is connected to the exit passage 5.
When the pressure regulating means 4 is constituted by a single pressure regulating valve, when such defective conditions wherein the valve body 10 is kept opened or closed are encountered, the fuel pressure in the fuel injection passage 2 may be decreased under or increased over the predetermined value. Therefore, a redundant pressure regulating means in the fuel injection apparatus for an engine provided with a plurality of pressure regulating valves is proposed in JP-U-6-83951. According to the redundant pressure regulating means, such an operational defect wherein one of the pressure regulating valves is kept opened by a breakdown or some other reasons, the other pressure regulating valve regulates the fuel pressure instead.
In the valve construction provided with a plurality of pressure regulating valves, when any one of the pressure regulating valve does not operate properly, another substitute pressure regulating valve carries out the fuel pressure regulation, and thus no problem is outwardly presented. Granted that it is adapted to notify an occurrence of defective conditions, it is difficult to recognize which valve is defective. Therefore, it has been desired to enable the operator to grasp the state of the defective conditions accurately.
Furthermore, since such defective conditions occur due to breakage of a diaphragm or damage of a spring in many cases, when the type which opens or closes the valve by depression at the engine manifold as shown in FIG. 3 is employed, it is desired to prevent fuel which entered into the air chamber 15 due to breakage of the diaphragm or the like from escaping from the air chamber. Accordingly, it is an object of the present invention to provide a pressure regulating means which realizes such requirements.
In order to solve the problem described above, the first aspect of the present invention provides a fuel injection apparatus for an engine including a fuel pump for pumping fuel from a fuel tank to a fuel injection passage, an injector for injecting fuel from the aforementioned fuel injection passage, and pressure regulating means disposed between the fuel injection passage and the fuel tank for regulating the fuel pressure in the aforementioned fuel injection passage at a constant value. The pressure regulating means includes a first pressure regulating valve and a second pressure regulating valve wherein the first pressure regulating valve and the second pressure regulating valve are connected at the entrances thereof to the aforementioned fuel injection passage via a first and second orifice, respectively The aforementioned first pressure regulating valve and the second pressure regulating valve are connected at the exits thereof to the aforementioned fuel tank, respectively. A first pressure sensor is provided for detecting the fluid pressure applied on the downstream of said first orifice. A second pressure sensor is provided for detecting the fluid pressure applied on the downstream of said second orifice. Failure diagnostic means are provided for notifying of the occurrence of the defective conditions to a driver by a predetermined display or the like when the pressures detected by the aforementioned first pressure sensor and the second pressure sensor are different.
The present invention includes the pressure regulating means having a diaphragm type fuel pressure regulating valve, an air chamber defined by the diaphragm in the interior of the fuel pressure regulating valve, a outside communication passage for communicating between the outside and the air chamber, and an escape prevention valve for closing the outside communication passage when fuel is entered into the air chamber.
The present invention includes the escape prevention valve that is a float type that is actuated by a buoyancy of fuel.
According to the present invention, the first and the second pressure regulating valves are provided as pressure regulating means, and the first and the second sensors are provided for the first and second pressure regulating valves, respectively. When the first and the second pressure regulating valves are normally operated, the equivalent fluid pressures are applied to the respective pressure regulating valves positioned downstream of the respective orifices. Therefore, the fluid pressures detected by the first and the second sensors are almost the same. Thus, the failure diagnostic means determines that the apparatus is in the normal condition.
When malfunction occurs in either one of the pressure regulating valves, the respective pressure regulating valves are connected to the fuel injection passage via the first and the second orifices, respectively. As a consequent, there is a difference between the fluid pressures applied on the respective fuel pressure regulating valves positioned downstream of the respective orifices. Therefore, the failure diagnostic means determines that the apparatus is in the abnormal condition from the pressure difference between the fluid pressures detected by the first and the second sensors, and thus allows the other normal pressure regulating valve to continue regulating operation, and notifies the operator of the occurrence of the defective conditions and which one is defective. Therefore, the operator can recognize the occurrence of the defective conditions and the part where such defective conditions are encountered immediately, and thus can take an adequate countermeasure.
According to the present invention, even when fuel enters into the air chamber because of a breakage of a diaphragm, further outflow of fuel through the outside communication port can be prevented since the escape prevention valve closes the outside communication port of the air chamber.
According to the present invention, since the escape prevention valve is provided, the escape of fuel may be prevented. In addition, since the escape prevention valve is a float utilizing the buoyancy of the fuel, the escape prevention valve may be constructed in a simple structure.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.